It depends on what you mean by 'graphics are poor.' If you mean the quality of the Sprites, you can make your own sprites using programs like Adobe Illustrator or the many 'free' image manipulation tools. The quality of those images is dependent on how good your graphic illustration skills may be.
If you mean background images, the answer is the same.
"Put more graphics on", The tutorials show how to add resources (Media). You can put as many graphic images on as you want, just remember, you do NOT want high resolution images in your projects...the device screens are small and large images have more pixels then required.
Regards,
Steve